Recuperative roasting-kiln.



J. ZBLLWEGER.

REGUPERIATIVE ROASTING KILN. APPLICATION FILED JAN. 9, 1911.

1,017,839. Patented Feb.20,1912.

I www A n zz /9 l figg/{75;} i

INvEN'ToR;

COLUMBIA PLANOGRAPH CO..w^5||\NGToN. D. C

UNITED STATES PATENT OFFICE.`

JOHN ZELLWEG-ER, OF ST. LOUIS, MISSOURI.

RECUPERATIVE ROASTINGr-KILN.

To all 'whom it may concern:

Be it known that I, JOHN ZELLWEGER, a citizen of the United States,residing at St. Louis, Missouri, have invented a certain new and usefulImprovement in Recuperative Roasting-Kilns, of which the following is afull, clear, and exact description, such as will enable others skilledin the art to which it appertains to make and use the same.

This invention relates to kilns such as are used for roasting ore.

When ore, such as zinc sulfid known as zinc blende is heated in aroasting kiln in the presence of air, its components are oxidized intothe products zinc oxid and sulfur dioxid. If the sulfur dioxid is to beutilized in the manufacture of sulfuric acid it should form at least 5%of the total roast gases treated for such purpose, and should beassociated with little or no carbonaceous gases such as carbon dioxid.Mutile kilns produce the results above-mentioned but such kilns are notentirely satisfactory on account of the excessive expense in furnacematerial, fuel and labor. Y

The main object of my present invention is to provide a mechanicalroaster which is so designed that a large percentage of sulfur dioxidwill be separated from the fire gases in the kiln and delivered inconcentrated form without unnecessary dilution. To this end I havedesigned a kiln which is so constructed that the carbonaceous fire gasesare withdrawn from the hot part of the kiln chamber which contains theore that is nearly roasted, and fresh air, is supplied to the fresh oreso as to oxidize the fresh ore under the iniiuence of heat produced bythe burning ore, the fresh air being preferably heated before it issupplied to the fresh ore so as to accelerate the oxidizing process.

Another object is to provide a roasting kiln having a recuperator thatcauses part of the heat from the outgoing fire gases to be returned backinto the kiln chamber, the recuperator preferably consisting of fireflues and air chiots arranged adjacent each other so that the heat whichis conducted through the walls of the fire flues will heat the air inthe air ducts and suitable suction-producing devices for causing freshair to travel through said air ducts and enter the cooler part of thekiln chamber and also causing the fire gases in the kiln chamberSpecification of Letters Patent.

Application filed January 9, 1911.

Patented Feb. 20, 1912.

Serial No. 601,709.

to be withdrawn therefrom through said fire flues.

Another object of my invention is to provide a roasting kiln which is sodesigned that the heat which is conducted through the roof and hearth ofthe kiln chamber is utilized to heat air that oxidizes the fresh ore,and also to heat the fuel that is used to desulfurize the partiallyroasted ore, the fuel being preferably supplied to suitable burners bymeans of fuel iues arranged under the hearth of the kiln chamber.

Another object is to provide a roasting kiln having means of novelconstruction for preventing the ore along the sides of the hearth fromcooling. And still another object is to provide an ore-stirringapparatus of novel construction.

Other object-s and desirable features of my invention will behereinafter pointed out.

Figure 1 of the drawings is a vertical transverse sectional view of anannular recuperative roasting kiln constructed in accordance with myinvention, taken' on approximately the line I-I of Fig. 2, said viewalso showing a vertical longitudinal section of the kiln chamber andrecuperator taken through the center of same, as indicated by thesection lines II-II of Figs. 1 and 2; Fig. 2 is a horizontal sectionalview, the lower right hand part being taken on the line III-III of Fig.1, the left hand parton the line IV-IV of Fig. 1, and the upper righthand part on the line v V of Fig. 1; Fig. 3 is a longitudinal sectionalview of the ore-stirrer; Fig. 4c is a cross sectional view of saidstirrer; Fig. 5 shows part of the shaft on which the stirrer is mounted;and Fig. 6 illustrates the key bar that secures the stirrer to itsshaft.

I have herein illustrated my invention embodied in an annular roastingkiln of the type shown in my prior U. S. Patent No. 976,769, datedNovember 22, 1910, but I wish it to be clearly understood that mypresent invention is not limited to annular kilns for it is applicableto various other types of kilns.

Referring to the drawings which illustrate the preferred form of myinvention, A designates a segmental annular kiln chamber or roastingchamber provided at its receiving or charging end with a door 1 and atits rear end, or discharge end, with a door 2, both of Which arenormally closed. The inner side Wall 3 of said kiln chamber is providedwith a horizontally disposed slot for receiving a radially-disposedstirrer shaft 1 having a stirrer S which moves the ore over the hearth,and a truss B is provided for supporting the arched roof 5 of the kilnchamber, the outer Wall and the hearth of said kiln chamber beingdesignated by the reference characters 6 and 7, respectively. Thehorizontal slot in the inner side Wall 3 of the kiln chamber is closedby the annular shield plate 8 through which the stirrer shaft tprojects, and suitable means is provided for sealing the edges of saidshield plate so as to prevent air from entering` the kiln chamberthrough the horizontal slot which said shield plate covers. The shieldplate 8 is braced by a number of horizontally-disposed brace' rods 9that project radially from a bearing member 10 which is supported on avertical shaft 11 at the center of the kiln, and the lower edge of saidshield plate rests on rollers 12 Which are rotatably mounted onstationary bearings arranged outside of the inner Wall 3 of the kilnchamber. The stirrer shaft 4 is also journaled in the bearing member 10,and any suitable means may be used for rotating said shaft and forcausing said shaft to travel around the vertical shaft 11 as an axis soas to move the stirrer S longitudinally of the hearth on Which the orerests. The means herein shown for rotating` the stirrer shaft consistsof a driven gear 13 that meshes with a miter gear 14 on the stirrershaft 4, and the means for bodily moving said stirrer shaft around thekiln consists of a traction gear 15 on said shaft that meshes with acircular cog track 16. Most of the parts previously described aresimilar in general characteristics to the corresponding parts of thekiln shown in my patent above referred to and operate in a similarmanner, but I will now describe the features that distinguish my presentinvention from the kilns that have heretofore been in use.

Instead of arranging the burners throughout the entire length of thekiln chamber, as has heretofore been the general practice, I arrange theburners in such a manner that the ore is subjected to artificial heat orlire gases only When it is traveling through the latter portion or rearportion of the kiln chamber after most of the sulfur has been extracted.The ore in the front portion of the kiln chamber is not subjected toartiicial heat except When the kiln first started but air is supplied tothis portion of the kiln chamber to oxidize the fresh cre and thusproduce heat, this heat gradually accumulating and raising thetemperature of the ore to such a degree that the ore in the presence ofair loses more than 80% of its sulfur under the influence of its ownheat during its travel over the front portion of the hearth. Then thecontents of the sulfur in the ore has been reduced to about 8%, the heatproduced by its oxidation has to be supplemented by heat from fuel, andtoward the end of the-roasting process it has to be maintainedl entirelyby artificial heat from fuel. Therefore, I arrange the burners in thekiln chamber in such a manner that the ore is subjected to artificialheat only when it is traveling through the rear portion of the kilnchamber, and I have designed the kiln in such a manner that the firegases from this artificial heat do not mingle with the sulfur gasesextracted from the ore that is traveling over the front portion of thehearth. Consequently, my improved kiln not only delivers a largerpercentage of the sulfur gases in suitable condition to be used in themanufacture of sulfurie acid, but it is also inexpensive to operate.

The burners 17 are preferably arranged in ledges or curbs 1S at thesides of the hearth 7, as shown in Fig. 1, and in the rear portion ofthe kiln chamber A over which the recuperator extends, as hereinafterdescribed. The front portion of the kiln chamber A, shown in the lowerrighthand corner of F ig. 2, is not provided With burners that are usedwhen the kiln is in full operation, but this portion of the kiln chamberis provided With auxiliary burners 17EL that are used when the kiln isfirst started and Which are cut out of service after the kiln chamberhas become heated. The burners 17 and 17a communicate with fuel fines 19and branch flues 19a arranged under the hearth 7, as shown in Fig. 1,and air ports 2O are arranged adjacent the burners, as shown in Fig. 1,to supply air thereto, each burner being preferably provided With asuitable controlling valve Q1 of any preferred type or design, thevalves herein shoivn being slide valves that are provided With handles21a. l/Vhile I prefer to arrange burners at both sides of the hearth asingle set of burners at one side of the hearth could be used ifdesired, and instead of arranging said burners in the ledges or curb atthe sides of the hearth they could be arranged in the side walls of thekiln chamber. I prefer the construction herein shown, however, for itfacilitates the introduction of the tire into the kiln chamber and thecurbs 1S hold the ore far enough aivay from the side Walls of the kilnchamber to prevent the ore from cooling.

The recuperator consists of a plurality of segmental-shaped fire fines22, and air ducts' Q3 arranged over the roof 5 of the latter half orrear portion cf the kiln chamber in Which the greatest degree of heat isattained, the air ducts being arranged between the fire flues andextending parallel to same.

These fire flues 22 communicate with a chimney 24 or other suitablesuction-producing device, as shown in Fig. 2, so thatthe fire gases inthe rear portion of the kiln chamber will be drawn upwardly throughports 22aL in the roof of the kiln chamber, thence longitudinallythrough said iire iues in the direction indicated by t-he arrows to theports 22b which lead to the chimney 24, the outlet ports 22a for thefire gases being located adjacent the middle of the kiln chamber. Thefront ends of the air ducts 23 aie open, as shown in Fig. 1, so that airwill pass into said ducts and travel through same in the directionindicated by the arrows in Fig. 2, to inlet ports 23a that are formed inthe roof of the kiln chamber at a point intermediate the front end ofsaid chamber and the outlet ports 22a through which the fire gasesescape from the kiln chamber. The sulfur gases extracted from the ore inthe front portion of the kiln chamber are withdrawn from said chamber bymeans of an exhaust fan 25 or other suitable suctionproducing devicethat communicates with a discharge port 26 formed in the roof of thekiln chamber adjacent the charging end of same, as shown in Fig. 2, saidsuction device also operating to draw the air through the air chiots 23of the recuperator and into the kiln chamber.

lhile I Aprefer to construct the kiln in the manner herein shown, itwill, of course, be understood that the length of the iire flues and airducts of the recuperator, and the location of the ports in the roof ofthe kiln chamber could be varied without departing from the spirit of myinvention. Therefore, I do not wish the terms front and rear portion ofthe kiln chamber or hearth to be construed as meaning the front and rearhalves of the kiln chamber or hearth.

'Ihe two exhausting or suction devices 24 and 25 produce a neutral Zonein the kiln chamber A between the outlet ports 22a for the fire gasesand t-he inlet port-s 23L for the fresh air, in which neutral zone theow of gases is slow and changeable in direction if the fresh air supplyis limited. By admitting a surplus of air, however, part of this airwill ow to the ire ports 22a and leave the kiln chamber while the otherand larger part of the air will flow over t-he fresh ore on the frontportion of the hearth and oXidize it. It will thus be seen that the tiregases dov not mingle with the sulfur gases in the front portion of thekiln chamber for said fire gases are withdrawn from the kiln chamber ata point about halfway between the ends of same, and the sulfur gases arewithdrawn from the kiln chamber at the front or charging end of same.rIhe withdrawal of the hot ire gases from the middle portion of the kilnchamber would cause a loss of heat if said gases were dischargeddirect-ly through a chimney, but in my improved kiln the heat from saidgases is utilized to heat fresh air that is supplied to the kiln chamberto oXidize the fresh ore, a large part of the heat in the out-going firegases passing through the partition walls between the fire flues 22 andthe air ducts 23 and thus being taken up by the ingoing air. By havingthe fire gases and the fresh air low in opposite directions through therecuperator it is possible to heat the ingoing air to near thetemperature of the outgoing fire gases, especially if the recuperator isarranged over the hot part of the kiln chamber, as herein shown. Byintroducing fresh heated air into the front portion of the kiln chamber,the desulfurization of the ore is greatly accelerated and consequentlymore sulfur is saved.

Any suitable kind of stirrer can be used but I prefer to use a stirrer Sof the kind herein shown because such a stirrer distributes the oreevenly over the hearth and does not work it to one side o-r the other.Said stirrer consists of a plurality of sections 27 that are adjustablymounted on the shaft 4, each of said sections having a hub that isprovided with radially projecting blades. The shaft 4 is provided with aseat or guideway for a key-bar 28 that consists practically of a numberof keys integrally connected together, the inner one of these keyshaving parallel sides, the second one a slight taper, and the third onetwice the taper of the second. The hubs of the sections 27 have keyseats which conform to the general shape of the keys on the key-bar butthe width of the key seats in the second and third sections is slightlygreater than the width of the keys which coperate with said sections.The key seat in the shaft 4 is not tapered but it is so designed thatthe key-bar can be moved longitudinally of the shaft, the means hereinshown for adjusting the key-bar consisting of a threaded eXtension 28aon the key-bar passing through a yoke 29 on the shaft and having a nut28b mounted thereon. 'By moving the key-bar inwardly the wings on thesecond section will be arranged at a dierent angle with relation to thewings of the first section and the wings of the third section will bearranged at still a greater angle with relation to the wings of thefirst section, the pressure which the ore eXert-s on the wings or bladesof the stirrer operating to hold the different sections of the stirrerin adjusted position.

While I prefer to construct the recuperator in the manner previouslydescribed, it will, of course, be understood that the same result couldbe obtained *in various other ways. For example, a large air duct orflue could be arranged between the roof of the kiln chamber and a fireflue, and suitable outlet ports or passageways provided for permittingthe fire gases in the rear portion of the kiln chamber to enter saidfire flue, and suitable inlet ports provided for causing jets of air toenter the front portion of the kiln chamber. Furthermore, while I haveherein shown the kiln chamber as a continuous chamber having twoportions, which for the sake of clearness I have designated the frontportion and the rear portion, I do not wish it to be Vunderstood that mybroad idea is limited to the exact construction herein shown for thesame results could be accomplished in various other ways. Therefore, Iwish the terms front and rear portions to be construed as meaning thecool and hot portions of the kiln chamber respectively, irrespective ofwhether said two portions are arranged in the same horizontal plane orin different horizontal planes.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

l. An ore roasting kiln comprising a kiln chamber, means for subjectingore in a portion of said kiln chamber to the radiating heat of firegases within said chamber, means for withdrawing said fire gases fromthis portion of the kiln chamber, means arranged outside of the kilnchamber for causing fresh air to be heated by the outgoing fire gasesand to be introduced into a different portion of the kiln chamber so asto oxidize the ore and produce heat therein, means for withdrawing thegases produced by the oxidation of said ore, and means for moving theore through said kiln chamber.

2. An ore roasting kiln comprising a kiln chamber, means for supplyingair to the ore in the front portion of said kiln chamber so as tooxidize same, means for thereafter subject-ing said oxidized oretoradiating heat from tire gases within said chamber, and means forpreventing said fire gases from mingling with the gases in the kilnchamber that are extracted from the fresh ore during the process ofoxidizing same.

8. An ore roasting kiln comprising a kiln chamber, means for conveyingore through said kiln chamber, means for extracting the main portion ofone of the constituents of said ore in one part of the kiln chamber andconducting it .out of said kiln chamber, means for subsequentlysubjecting the ore to the radiating heat of fire gases within anotherpart of the kiln chamber so as to roast said ore, and means forpreventing the tire gases inside of one part of the kiln chamber from-mingling with the gases inside the other part of the chamber that areextracted from the ore in this part of the kiln chamber.

4. An ore roasting kiln, comprising a continuous kiln chamber that isadapted to receive ore, means for roasting the ore in one part of saidchamber in the presence of air so as to oxidize the components of same,means for collecting and withdrawing from the kiln chamber the majorportion of one of the components produced by oxidizing the ore, meansfor causing said ore to be subsequently acted upon by fire gases withinthe chamber, and means for preventing the admixture in the kiln chamberof the fire gases and the gases that are extracted from the ore duringthe first stage of the process. v

5. An ore roasting kiln, comprising vva kiln chamber that is adapted toreceive ore, means for introducing fire gases into the rear portion ofsaid chamber so as to cause the ore in this portion of the chamber to beroasted by the heat which radiates from the lire gases within thechamber, means outside of said chamber for transferring part of the heatfrom said fire gases to air, means for supplying this heated air to thefront portion of the chamber to oxidize the ore therein, and means forpreventing the roast gases in the front portion of said kiln chamberfrom mingling with t-he fire gases Within the rear portion of saidchamber.

6. An ore roasting kiln, comprising a kiln chamber that is adapted toreceive ore, means for introducing fire gases into the rear portion ofsaid chamber so as to cause the ore in this portion of the chamber to beroasted by the heat which radiates from the fire gases within thechamber, means out-side of said chamber for transferring part of theheat from said fire gases to air, means for supplying this heated air tothe front portion of the chamber to oxidize the ore therein, and meansfor withdrawing from the front portion of the kiln chamber the gasesthat are produced by oxidizing the ore therein.

7. In an ore roasting kiln, a kiln chamber through which ore isconveyed, means for supplying fire gases to the rear portion of saidchamber, means for extracting said ire gases from the rear portion ofsaid chamber, and means for causing air to absorb the heat from saidextracted fire gases and flow into the remaining or front portion ofsaid chamber so as to oxidize the ore therein.

8. An ore roasting kiln, comprising a kiln chamber through which ore isconveyed, burners Vin the rear portion of said chamber which supply liregases thereto, fire iues communicating with outlet ports for said firegases arranged intermediate the ends of said kiln chamber, said fireflues being located over the kiln chamber, means for causing the liregases to travel outwardly through said flues, and means for causingfresh air to travel adjacent said flues and ab sorb heat from same andthen pass into the front portion of the kiln chamber so as to oxidizethe ore therein.

9. In an ore roasting kiln, a kiln chamber through which ore isconveyed, burners in the rear port-ion of said chamber for supplyingfire gases thereto, a recuperator consisting of lire flues and air ductsarranged adjacent each other, said fire flues communicating with outletports in the kiln chamber through which the fire gases from the rearpart of the kiln chamber escape and said air ducts communicating withinlet ports through which fresh air is admitted to the front portion ofthe kiln chamber, and means for inducing drafts through said lire fluesand air ducts. j

10. An ore roasting kiln, comprising a kiln chamber through which ore isconveyed, burners arranged in the rear portion of said chamber forsupplying fire gases thereto, a recuperator arranged over this portionof the kiln chamber and consisting of parallel lire flues and air ductsarranged in proximity to each other, the roof of the kiln chamber beingprovided with outlet ports for the fire gases that communicate with saidfire flues and also inlet ports for the fresh air that communicateswithsaid air ducts, means communicating with the opposite ends of said fireflues for inducing a draft through same, and a suction-producing devicethat communicates with the charging end of said kiln chamber.

11. In a roasting kiln, a kiln chamber having inlet ports for fire gasesand for air, a collective outlet port for the fire gases arranged abouthalfway between the ends of said chamber, inlet openings for airarranged near said collective outlet port, and an outlet port for sulfurgases adjacent the charging end of said chamber, each of said outletports communicating with separate exhaust or suction-producing devices.

12. In a roasting kiln, a kiln chamber having inlet ports for fire gasesto part of the kiln chamber, an air duct which communicates at one endwith the atmosphere and at its other end with the remaining part of saidkiln chamber, and an outlet port for said fire gases arranged somedistance away from the point at which said air duct communicates withsaid chamber. Y

13. In a roasting kiln, a kiln chamberhaving inlet ports for gases andfor air, a recuperator located over the rear part of said chamber andhaving fire flues and air ducts arranged adjacent each other, the fireflues connecting at one end with the kiln chamber at a pointintermediate the ends of same and at the other end with asuctionproducing device, and the air duct-s of said recuperatorcommunicating at one end with the atmosphere and at the other end withthe front part of the kiln chamber at a point between the charging endof the kiln chamber and the point where said fire llues connect withsaid chamber.

14. In a roasting kiln, a recuperator located over a part of the kilnchamber that is heated and having lire flues and air ducts arrangedadjacent each other, the fire lues connecting the heated part of thekiln chamber with a chimney and the air ducts connecting the atmospherewith a different part of the kiln chamber which is relatively cooler andthrough this chamber with an eX- haust fan or similar device.

15. In a roasting kiln, a kiln chamber having curbs or ledges projectingfrom the side walls toward the hearth, and burners arranged in saidcurbs or ledges.

16. In a roasting kiln, a kiln chamber having curbs or ledges arrangedadjacent the sides of the hearth so as to hold the material away fromthe side walls of the kiln chamber, and burner ports arranged in saidledges that communicate with a fuel Hue.

17. In a roasting kiln, a stirrer comprising a rotatable shaft, aplurality of members adjustably mounted on said shaft and each providedwith radially projecting wings that engage the material on the hearth ofthe kiln, said members being adapted to be rotated relatively to theshaft and to each other so as to arrange the wings on one member at adifferent angle with relation to the wings of an adjacent member, and adevice for securing all of said members to the shaft.

18. A stirrer for a roasting kiln, comprising a rotatable shaft, aplurality of members mounted on said shaft and each consisting of a hubprovided with a plurality of radially projecting wings, and a key-barfor securing all of said members to said shaft, said key-bar and membersbeing so constructed that the members can be a'djusted so as to arrangethe wings of onev member at a different angle with relation to the wingsof an adjacent member.

19. An annular roasting kiln, comprising a segmental-shaped kilnchamber, means for conveying material through said chamber, means forsupplying fire gases to the rear portion of said chamber, a recuperatorarranged over the roof of the rear portion of said chamber andconsisting of fire flues and air ducts arranged adjacent each other,outlet ports inthe roof of said chamber that communicate with said firellues, and inlet ports arranged intermediate said outlet ports and thecharging end of said chamber for establishing communication between saidair ducts and the front portion of the kiln chamber, an exhaustingdevice communicating with the outer ends of said lire lues, and anexhausting device communicating with the charging end of said kilnchamber.

20. An annular ore roasting kiln, comprising a segmental-shaped kilnchamber. means for feeding -ore over the hearth of said chamber, a fuelflue arranged under a portion of said hearth, burners communicating withsaid 'fuel time for supplying lire gases to the rear portion of saidkiln chamber, a recuperator consisting of discharging fire flues thatcommunicate With the rear portion of said chamber, and air inlet portsthat communicate with the front portion of said chamber, asuction-producing device communicating with said fire flues, and asuction-producing device that communicates With the charging end of saidkiln chamber.

21. In an annular roasting kiln, a substantially annular orsegmental-shaped kiln chamber provided in one of its side Walls with ahorizontally disposed slot, an annular-shaped shield plate for closingsaid slot, a stirring apparatus comprising a member that projectsthrough said shield plate into said kiln chamber, and a plurality offriction-reducing devices mounted in stationary bearings and operatingto support said shield plate.

22. In an annular roasting kiln, a substantially annular orsegmental-shaped kiln chamber provided in its inner Wall with ahorizontally disposed slot, an annularshaped shield plate for closingsaid slot, a stirring apparatus comprising a member that projectsthrough said shield plate into said kiln chamber, a plurality of rollersmounted in stationary bearings adjacent the inner Wall of said kilnchamber for supporting said shield plate, a rotatable bearing memberarranged adjacent the center of the kiln, and braces for connecting theshield plate to said bearing member.

23. In an annular roasting kiln, a sub.- stantially annular' orsegmental-shaped kiln chamber provided in its inner Wall With ahorizontally disposed slot, an annularshaped shield plate for closingsaid slot, a plurality of frictionreducing devices mounted in stationarybearings arranged adjacent the inner Wall of said kiln chamber forsupporting said shield plate, a rotatable bearing arranged adjacent thecenter of the kiln and provided with radially disposed braces Which areconnected to said shield plate, a stirrer arranged in said kiln chamber,la shaft for said stirrer supported by said shield plate and rotatablebearing,

and means for moving said shield plate in a circular path.

24. A roasting kiln, comprising a kiln chamber, means for introducingiire into the rear portion of said kiln chamber, a fire flue, an airduct or flue arranged on top of the roof of said kiln chamber so as tocause the air which passes through same to become heated, means forpermitting the air in said air duct to enter the front por tion of thekiln chamber, and means for creating a draft or suction in the frontportion of the kiln chamber.

25. An ore roasting kiln, comprising a kiln chamber, means for causingfire gases to travel through a port-ion of said chamber and then escapetherefrom so as to heat the orc in this portion of the kiln chamber',means for utilizing heat from the outgoing fire gases for heating airwhich is supplied to a different portion of the kiln chamber thatcontains fresh ore, this heated air acting to oxidize the fresh ore andproduce heat in this portion of the kiln chamber, means for collectingthe gases produced by the oxidation of the ore, and means for moving theore through the kiln chamber so as to cause the oxidized ore to besubsequently heated by the fire gases first referred to.

26. An ore roasting kiln comprising a kiln chamber, means for causingore in a portion of said kiln chamber to be acted upon directly byartificial heat Within said chamber, a flue through Which the spent heatcan escape, means arranged outside of the kiln chamber for transferringpart of this spent heat to air and supplying this heated air to ore inthe remaining portion of the kiln chamber so as to oXidize the ore andproduce heat therein, means for Withdrawing the gases produced by theoxidation of said ore, and means for moving the ore through said kilnchamber.

In testimony whereof I hereunto aiiix my signature in the presence oftwo Witnesses, this sixth day of January 1911.

lVnLLs L. CHURCH, y GEORGE BAKEWELL.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents,

Washington, D. C.

